Exploring Losses in Tantalum Transmons*

In this talk we explore the dominant loss mechanisms in state-of-the-art tantalum transmons. We iteratively modify our fabrication procedure and examine the effect on qubit coherence through temperature dependent depolarization curves and spectroscopic pulse sequences designed to saturate two-level-systems. This allows us to explore the interaction strength and corresponding loss rate of the spurious fluctuators. In order to quantify the relative strengths of quasiparticle, two-level-system, and other loss mechanisms we measure the temperature dependence of transmons in different geometric and frequency regimes.